This invention relates to an antivibration device mainly used for supporting and bearing an automotive engine, etc.
A liquid-sealed type of antivibration device is known in the art as a mount for bearing a vibration generator such as automotive engine so as not to transmit its vibrations to the vehicle body. This antivibration device is composed of a main body fitting to be attached and secured to a support side, an upper attachment fitting to be attached to a vibration generator side such as an engine, a thick-walled vibration-isolating base of rubber-like elastomer configured as a generally truncated conical shape interconnecting the former two, a diaphragm opposing to the vibration-isolating base fitted to the lower side of the main body fitting, an interior room between both the previous elements defined as a liquid-sealed chamber, and a partition member comparting the liquid-sealed chamber into two liquid chambers on the vibration-isolating base side and the diaphragm side, both liquid chambers communicating with each other through an orifice. And it is adapted to perform a vibration damping function and a vibration isolating function due to a liquid fluidization effect between both liquid chambers through the orifice and a vibration-absorbing effect of the vibration-isolating base.
Such an antivibration device is generally further provided with a stopper mechanism for restraining a large displacement of the upper attachment fitting beyond a definite magnitude owing to deformation of the vibration-isolating base accompanied by vibrations. With the conventional device, the stopper mechanism is constructed so that a stop flange projecting in a radial direction is provided to the upper attachment fitting, on the one hand, and a box shaped stopper fitting extending from outboard of the vibration-isolating base to above the flange is fixed to the main body fitting, with the top edge of the stopper fitting being bent inwardly to form a stopper portion, which is located between the flange and the vibration generator side member such as a bracket attached upwards of it, on the other hand. Upon a large displacement in the vertical direction, the stopper portion is thus adapted to abut on the stop flange of the upper attachment fitting and the vibration generator side member such as bracket, thereby performing a stopper action. A stopper rubber may be formed by vulcanization integrally with the stopper portion of the stopper fitting for the purposes of shock absorbing when abutting on the vibration generator side member and the stop flange.
In the abovementioned structure, the stopper fitting serves also to intercept a radiation heat or hot air from intruding into the vibration-isolating base portion. That is, if the vibration-isolating base is heated by radiation heat or the like, there arises a problem such that its characteristics change and for that reason, the aforementioned structure is adopted.
However, the stopper fitting is made of a pressed steel plate with the conventional device above, which is constructed so as to cover the overall vibration-isolating base assuring a relatively large, generally truncated conical form only with this stopper fitting. As a result, the weight of the stopper fitting itself becomes heavy, which is obstructive to rendering the weight of the antivibration device lighter. This is also true where the stopper rubber is integrally molded by vulcanization.
On the other hand, it was proposed to adopt a stopper fitting whose cylindrical body is partly cut out from the viewpoints of easiness in fixing working by crimping fastening and in assembling work. In this case, the stopper fitting can be rendered lightweight, but radiation heat or hot air enters through the cutout portion into the vibration-isolating base inside the stopper fitting. Thus there was a problem in the respect of heat intercepting effect.
The present invention has been made in view of the problems with the antivibration device provided with the stopper mechanism as described above and is contemplated providing an antivibration device which is lightweight and excellent in heat interception effect by constructing a stopper fitting in a partly cutout form so that it can be made more lightweight and concurrently can secure to intercept radiation heat from another components.
This invention relates to an antivibration device comprising a main body fitting having a cylindrical drum part, an upper attachment fitting adapted to be connected to a vibration generator side, a vibration-isolating base made of rubber-like elastomer interconnecting an upper end opening of the main body fitting and the upper attachment fitting, a stopper fitting coupled to the main body fitting, the stopper fitting assuming a generally cylinder form with a partly cutout portion and extending upwardly and outboard of the vibration-isolating base, the stopper fitting being at its upper end part bent inwardly to form a stopper portion performing a stopper action against a large vertical displacement of the upper attachment fitting. And in order to solve the aforementioned problems the device is characterized in that the stopper fitting is fitted with a stopper rubber member by vulcanization molding, the stopper rubber member extending from a top surface of the stopper portion to an outer surface of a side plate of the stopper portion, and a heat shield rubber membrane portion for plugging the cutout portion of the stopper fitting is formed by vulcanization integrally with the stopper rubber member.
According to this antivibration device, the stopper fitting is generally cylinder shaped with a partly cutout portion and the cutout portion is adapted to be plugged only by a heat shield rubber membrane portion integral with the stopper rubber member, so that it is possible to make the device more lightweight in comparison with a counterpart which comprises a stopper fitting of a usual cylindrical form covering the overall periphery of the vibration-isolating base and moreover it is possible to intercept the vibration-isolating base inside the stopper fitting from radiation heat from another components by the heat shield rubber membrane portion.
It is preferred that the stopper fitting be cut out in a range of nearly ⅓ to xc2xc of the entire circumference thereof and that the heat shield rubber membrane portion be formed so as to plug the cutout portion with a shape having approximately the same radius of curvature as that of the stopper rubber member.
Being formed in this manner, the appearance is good, a weight reduction and heat intercepting effect can be exhibited satisfactorily and a good stopper action is performed. That is, if the range of the cutout portion is narrower than the above, the effect of weight reduction is smaller whereas the range of the coutout portion is larger, the range in which the stopper acts to abut is smaller and the stopper action is not performed well. This is why the aforementioned range of the cutout portion is preferred.
In the aforesaid antivibration device, the heat shield rubber membrane portion can be formed, at its circumferentially central part, with a thinner membrane portion than both lateral portions thereof longitudinally contiguous with it. Consequently, in case where the stopper rubber member and the heat shield rubber portion are molded by vulcanization integrally with the stopper fitting, a configurative change and dimensional change due to vulcanization shrinkage of the rubber membrane portion can be absorbed by the thin membrane portion and it is possible to mold without being affected by the vulcanization conditions. Moreover the thin membrane portion functions as cushion means to any external interference and can exhibit the effect of resisting a curling and tearing of the rubber membrane portion.
The aforesaid thin membrane portion preferably has a circumferential width of up to ⅓ of the circumferential width of the rubber membrane portion and a thickness of up to xc2xd of the thickness of the other portions of the rubber membrane portion. Thereby it is possible to retain nearly the same radius of curvature as the stopper rubber member and to adapt to changes in shape and dimension upon vulcanization molding and any deformation due to external force only by the thin membrane portion by reason of its deformation. That is, if the width of the thin membrane portion is too large, the shape retainability is reduced and if the thickness of it is too large, its ability of coping with the changes in shape and dimension is reduced.
In the aforementioned antivibration device, the upper attachment fitting has a stop flange that is extended outwardly above the upside of the vibration-isolating base and the stopper portion of the stopper fitting is arranged between the flange and a vibration generator side to be fitted and secured above the flange so as to perform a stopper action against a large vertical displacement of the upper attachment fitting. Thus a good stopper action is performed.
This invention is particularly suitably utilized in a liquid-sealed antivibration device which further comprises a diaphragm made of rubber elastomer arranged at a lower side of the main body fitting so as to oppose the vibration-isolating base, a liquid-sealed chamber of an interior enclosed by the vibration-isolating base and the diaphragm, a partition member comparting the liquid-sealed chamber into two liquid chambers on the vibration-isolating base side and the diaphragm side, and an orifice through which both chambers communicate with each other.